1. Field of the Invention
The present invention relates to a network system.
2. Description of the Related Art
A failover is a technique of establishing a server network system having high reliability and availability. On the occurrence of a failure or abnormality occurring in a working server (system, network), the failover automatically changes over the processing from the working server to a redundant standby server (system, network). A cold standby failover technique may be adopted in a network system including a working server that provides a specific service, such as web service, and a standby server that performs another processing or stands in power-off condition. On the occurrence of a failure in the working server, the cold standby failover is implemented by resetting information (for example, an IP address) that is originally set in the working server, in the standby server.
A hot standby failover technique may be adopted in a network system including multiple servers that provide a specific service and a load balancer or a DNS (Domain Name System) server. On the occurrence of a failure in one of the multiple servers providing the specific service, a failover is implemented adequately according to the system configuration. In the system configuration with the load balancer, the failover is implemented by prohibiting the load balancer from sending a processing request to the server having the failure. In the system configuration with the DNS server, the failover is implemented by prohibiting the DNS server from notifying an IP address of the server having the failure.
The cold standby failover technique requires time for resetting the information to take over the specific service from the working server to the standby server and may thus cause a relatively long-time stop of the service. The hot standby failover technique allows for resumption of the specific service within a relatively short time but requires an additional network system component, such as the load balancer or the DNS server and may thus complicate the configuration of the network system.